The Fresh Air In-Forcer ventilation system from Tjernlund Products is designed for residential applications. The exterior hood and 90 CFM, 18-watt fan can be installed through a round, 4-inch exterior wall opening. The system can be controlled manually through a 115 VAC switched outlet, or through a plug-in timer. A standard 4-inch flex or metal duct can be used for ducting.
Tjernlund Products. http://tjernlund.com